The brochure included a letter from the king's son Prince Lindani saying his father King Mswati III backed the project. But as Richard E Grant learnt more about Michael Hart Jones's involvement in diamond and gold mines and private armies across southern Africa he became more concerned.

Secret filming

Hart Jones had also been involved in murky diamond deals with the junta which took power in Sierra Leone in 1997.

We posed as investors and secretly filmed him as he claimed that CARD had used it to save the lives of dozens of soldiers in Tanzania in 2001 "they were stretchered in virtually dead - as far as I was concerned they were dead". After the miracle cure "in two weeks they were up and about and back on track".

Richard E Grant reacted characteristically to the footage: "Dead people are now Lazarused from the grave - Bullshit".

Another director of CARD told us they inject goats with HIV and create antibodies which they inject into AIDS victims: "they kill the virus" he told us "and the people do very well".

AIDS expert Professor Michael Adler at University College Hospital said this was "not a tenable scientific approach" since even human antibodies fail to knock out HIV and there are no papers in scientific journals backing up their extraordinary claims.

Safety concerns

Goat serum emerged in the US 10 years ago but the Food and Drug Administration banned the use of the product on humans on safety grounds.

Thirty thousand Swazis need anti-retroviral drugs to keep them alive

In Britain the drugs watchdog have begun a criminal investigation of another firm involved in goat serum.

Hart Jones had extensive mining and military connections in a dozen African states and he tried to push goat serum in those countries.

He had an even better link to the Swazi royal family. His children go to the same private school as six of King Mswati's children.

He boasted how his kids at Buckswood School near Hastings had become "pally" with the prince. From there it was a short step to persuade the prince to become patron of CARD.

'Death sentence'

Back in Swaziland the need for real anti-HIV drugs rather than goat serum is obvious.

In 1995 life expectancy at birth was 58 years. It is now 34 and by 2010 it will be 29 all thanks to Aids. They are, as Richard E Grant says, "very vulnerable to a white man saying we have a cure".

Three hundred thousand Swazis are HIV positive - 30,000 at least desperately need anti-retroviral drugs to keep them alive. Only half of those are getting them.

Doctors and nurses everywhere told us they needed more resources to train health workers to get the drugs out to the people.

CARD put together a business plan. They wanted us to invest up to $98 million (£50 million) in their scheme. As a first stage they would carry out a drugs trial in Swaziland.

Forty seriously infected patients who should have been treated with anti-retrovirals would instead be given "goat serum".

Richard E Grant says that if he had become involved he would have been supporting something which was "effectively someone's death sentence".

Michael Hart Jones met us a second time in London.

Richard E Grant and our business correspondent Paul Mason appeared from a side room and challenged Hart Jones's claims.

Grant said "goat serum was basically snake oil" but Michael Hart Jones repeated that he had seen people brought in on a stretcher "and they've walked out of the clinic".

Challenged by Newsnight about the $98 million (£50 million) he had suggested we invest he said he was not in it for the money but to "try to help Africans".

The film can be seen on Newsnight on Friday at 2230 GMT on BBC Two in the UK and on the live Newsnight website.